Apparatus for and method of double web coating



Oct. 17, 1939. c. J. MERRILL 2,176,093

rr/muss FOR AND msrnon OF DOUBLE was comm:

Filed Api'il 12, 193'7 /4 '5 0/5034 lZa. 4%; e 7

Patented Oct.'17 1939 U'NITED STA-Tags mm'rus m AND METHOD or nounm wan con'rmo 'Carle J. Merrlll, Portland, Maine Application April 1a. 1931. Serial No. 136,356

This invention relates to the art of coating paper and more particularly to the coating of both sides of a traveling web or sheet and the distribution of a uniform coating over the sheet 5 by means of air-jets or air-doctors. I am aware that an air-doctor or air-jet has been employed to distribute and smooth coating materials on one side of a traveling web or sheet. My invention has to do with the use of air-jets in some- I what different form and arrangement for distributing coating on both sides of a traveling web,

:0 air-jet arrangement similar to Fig. 1.

Fig. 3' shows a third arrangement of coating applying means and the use of air-jets similar in design to Figs. 1 and 2.

Fig. 4 illustrates an arrangement for applying coating to traveling web, similar to that shown in Fig. 1, but a somewhat different means of airjet application for smoothing the applied coating.

Fig. 5 illustrates an arrangement similar to those of Figs. 1 and 4, but with a different means 0 of air-brush application.

I am committed to no particular method of applying the coating to the traveling web and the illustrations above referred to, are given simply to show conventional methods of applying coat- 5 ing to the web, after which it must be smoothed by some subsequent operation. Most, if not all,

of the conventional means of applying coating leaves a deposit of coating on the web of uneven thickness, with ridges and ripples and thick and 0 thin spots varying according to the condition of the coating on the application rolls.

It is the purpose of my invention to smooth out this uneven coating condition on the web, simultaneously, on both sides, by means of a jet of air properly directed against and on the web, with suitable means for disposingof the air impinged on'the web by the jet and what is more important, to dispose of the coating materials removed from the web and particularly, that part of the liquid coating'which may become mixed or atomized by the force of the air-jet.

The successful use of a jet of air for distributing and smoothing the coating material on a traveling web depends considerably on the mainstant position relative to the Jets on both sides of the" web. Where only one side of the web has been coated, it is readily possible to pass the uncoated side of the web over a guide or roll, which will holdit in a predetermined position in relation to which the location of the air-brush can be definitely fixed. With a double coated web, however, or one where the coating material has been applied to both sides, it is notposslble to pass this over a roll without seriously aifecting or completely destroying and disrupting the surface coating already applied. One particular and important feature of my invention is the-provision of means to hold the double coated web in proper position relative to both air-jets without mechanically contacting the sheet or the coating thereon.

Referring to Figs. 1, 2 and 3, the traveling sheet or web passes over guide roll I and between or partially around coating applicator rolls 2 and 2-a, These rolls serve'to apply the coating material to both sides of the traveling web l4. After leaving rolls 2 and 2-11, the web l4 passes between collector chambers 3 and 3-a, thence between air-Jets d and 4a, and over an auxiliary air-nozzle 6, and a deflector plate I.

The importance of maintaining the web I4 in central position between the air-jets 4 and 4--a has already been mentioned. This is accomplished by use of an air-jet 6 extending the entire width of the sheet or web, and immediately behind which is a deflector plate 1, which also extends the entire width of the sheet. Air, at high velocity, is forced through a narrow slot or orifice in the nozzle 6, passing under the sheet I l, and over the top surface of deflector I. The relation of the orifice in the nozzle 6 to the deflector plate 1, results in a thin film of air being projected between thesheet M and the deflector I, this sheet or film of air being uniform in thickness over the entire width of the sheet, thus holding the sheet It level andstraight.

It will be noted, that the outer end of the deflector 1 curves away or downwardly from the sheet M. This downward curve forms in eflect, a suction area, resulting from. the air passing between the sheet and the deflector, tending to hold a the sheet it down at this point, and preventing any tendency of the sheet to move upwardly. The thin jet or stream of air passing from the nozzle 6. over the highest point of deflector 1, effectively maintains a fixed distance between the deflector I and the sheet l4, without permitting or allowing either any part of the deflector 1- or ofthe nozzle 6 to come in contact with the sheet H, or the coating material thereon.

To further insure that the sheet be held in a central position between the air-jets 4 and 4-0, I provide deflector surfaces on each of the collecting pans 3 and H, these being shown at I2 and I2-a. It will be noted that the ends farthest from the jets 4 and 4a curve away from the sheet I4 in a manner similar to the deflector I, and the purpose of this and the operation and effect on sheet I4 of these deflector portions I2 and I2-a is the same as that already described of the deflector 1.

After leaving the nozzle 6 and deflector I, sheet I4 is drawn along by means not shown, which means imposes a lengthwise tension on the sheet or traveling web, stretching it tightly from its position over the deflector l to the applicator rolls 2 and 2a. Also, the web is held between the deflectors I2 and l2-a as above mentioned. A brake, or equivalent means, on the roll from which the web I4 is unwinding, enables the lengthwise sheet tension to be adjusted and maintained.

The sheet, having thus been held in a fixed position, relative to the collector chamber 3 and 3-0. and to the air-jets 4 and 4-a, it is thus possible to adjust the position of these respective parts so that air ejected from the slot or orifice in the nozzles 4 and 4a, may be impinged on the sheet and utilized to smooth out the coating imperfections. It will also remove any surplus coating in the form of ridges, ripples or thick portions and fill in and add coating on any thin areas.

One important and difficult problem is the provision of means for caring and disposing of the surplus coating material removed from the traveling web by the air-jets 4 and 4--a. Any surplus material left on the web by the applicator rolls is blown backward over the web, by the air-jets 4 and 4-a, and when too great an accumulation occurs, it is blown off the web in the form of fine drops or spray traveling with the air from the jets.

As this air isimpinged on the sheet at relatively high pressure and speed, it immediately expands and this together with its speed of travel, while efiective in smoothing the coating mate-- rial over sheet i4, must immediately be reduced in speed as soon as its work has been accomplished, in order that any intrained or atomized coating material may be collected and not blown out into the room or over the adjacent machinery causing waste and other difilculties.

In order that the air after leaving the jets, and doing its smoothing on its web surface may be slowed down in velocity, it is directed into collecting pans or enclosures 3. It will be noted in Figs. 1, 2 and 3 that these enclosures consist essentially of two parts. First, an entrance section I2 and I2a, one for the upper air-jet 4 and one for the lower air jet 4-a, and an impinging and expanding area at I5 and I5--a, continuing around the entire enclosed area 3 to the inside portion of the deflector section I2.

These deflector portions I2 have a dual purpose. First, they cooperate with their respective air-jets to form a smoothing area on the coated material on the sheet, and second, their inwardly curved portion near the center acts to draw the air away from the sheet together with any surplus coating material, and cause it to impinge on the inner surfaces at I5 and I5-a, the coating material collecting on these areas as well as other portions of the collector pans 3 and 3-41, from whence it may be drawn of! in. liquid. form to;

re-use. Normally, the surplus material in the upper collector 3, would flnd its way into the depressed section I6 in the deflector portion I2. In the lower collector pan 3a, this material would normally flnd its way andaccumulate in the bottom of this pan at I8a. By the time the air from the jets 4 and 4-a have passed into and about the collector pans 3 and 3-a the air velocity has been sufiiciently reduced so that any suspended coating material which the air may have contained has become lodged on some portion of the surface of the pans 3 and 3a., so that the air free of coating material can pass out from the ends oi these pans or be otherwise disposed of The arrangement shown in Figs. 4 and5, are primarily for the purpose of making the apparatus more compact and of reducing the distance from the applicator rolls 2 and 2a to the air nozzle 6 and deflector plate I, so that there will be a minimum length of traveling sheet or web l4, between these points efiecting a more rigid support of the web between the air-jets 4 and 4-a with the same degree of web tension.

A further advantage and improvement is secured by the arrangement of Figs. 4 and 5, in that the surplus coating material removed from the web I4 by the air-jets 4 and 4a, is first impinged directly on the applicator rolls 2 and 2-a, and carried back to either the application point at the end of pipe 8 in thecase of the upper roll 2 or back into the pan at the bottom of roll 2a.

In order to insure that none of the coating' material removed from the web by jets 4 and 4-41 escapes or is lost, the applicator rolls 2 and 2-a may be surrounded by collector pans 9 and 9-a, also forming a reservoir from which the roll 2-a obtains its coating material. The air, after leaving the jets 4 and 4a, passes between the edges I1 and I'I-a. of collector pans 9 and 9-a, passing upwardly or downwardly around the applicator rolls until its velocity is dispersed and the entrained coating material has become lodged eitheron the rolls or on the inside of collector pans 8 and 9-0. The air, free from coating material can then pass out thru the ends of the collector pans or be otherwise disposed of.

The arrangement of air removal and disposal in Fig. 5 is somewhat different than that shown in Fig. 4, in that two outlet passages I I1 and I t|-a are provided with sufllciently large area adjacent to the applicator rolls to permit the air from the jets to rid itself of entrained coating material before passing out thru these openings or passages l0 and l0-a.

This construction leaves the applicator rolls exposed for examination. Any entrained material in the air which may tend to pass out thru the upper passage III. will eventually, be precipitated on the sides of this. passage and drained back to the web or to the applicator roll. Any coating material which may be deposited on the walls of passage I ll--a can readily be collected at some low point in this passage.

65 The use of an air-jet or an air-doctor to smooth out the coating on one side of a sheet only, presents a fairly simple problem of jet and sheet location and 01 dispersing theair and collecting the surplus coating material.

However, the coating of both sides of a web or sheet simultaneously, and the smoothing of both of these coatings by air-jet methods, including the removal and collecting of the surplus coating mat rial presents new problems. These problems require the development of new methods and new v apparatus, which have been herein described.

What I claim is:

1. Apparatus oi the class described, comprising means for applying a coating of semi-liquid material to a traveling web, a pair of air-jets for smoothing said coating material over said web, a

pair of deflector plates cooperating with said air- Jets for maintaining said sheet in a predetermined position relative to said air-jets, said deflector plates forming in part an expansion chamher for air from said jets. 2. Apparatus for coating both sides of a traveling web, comprising means of applying coating material in semi-liquid form to both sides of said web, air-jets arranged to redistribute and smooth said coating materials simultaneously on both sides of said web, means for holding said traveling web in a predetermined position relative to said air-jets, said means comprising deflector plates forming a part of an expansion chamber, and air jet means for maintaining the web in a predetermined position relative to said first mentionedair jets.

3. Apparatus for applying coating materials in semi-liquid form to both sides of a traveling web, comprising means .for applying the coating materials to the web in excess of actual coating requirements, means comprising twoair-jets for removingthe surplus material simultaneously from both sides of the travelingweb, deflector plates on each side of the web cooperating with said air-jets to maintain the traveling web in a predetermined position relativeto said air-jets.

4. Apparatus for coating both sides of a traveling sheet or web, comprising means for applyingsaid coating material in semi-liquid form to both sides of said sheet or web, air-Jets opposed to the travel of the web, constructed and arranged to redistribute and smooth said coating materials simultaneously on both sides of said web, by directing the air counter to web travel, means for holding said traveling web in a predetermined position relative to said air-jets both before said web reaches said jets, and also after it has passed said jets, said holding means free of mechanical contact with said web or the coating material thereon.

5. Apparatus for applying coating materials in semi-liquid form to both sides 01' a traveling web, comprising means for applying-the coating materials to both sides of the web in excess of actual coating requirements, means comprising two airjets for removing the surplus coating material simultaneously from both sides of the traveling web, expansion chamberson each side of the traveling web for collecting surplus coating material' removed from the web by said air-jets, and deflector surfaces cooperating with said air-jetsto maintain the traveling web in a predetermined positionrelative to said jets. a

6. Apparatus for applying coating materials in semi-liquid form to both sides of a traveling web. comprising means for applying the coating materials to both sides or the web in excess of actual finished coatingrequirements, means comprising two air-jets for removing said surplus coating material said jets returning directly to said coatremainder of the surplus coating material re-.

moved fromthe web.

'7. The method or applying coating materials in semi-liquid form-to a traveling web, which consists in applying to both sides of the web coating materials somewhat in excess of actual coating requirements, of simultaneously removing said surplus coating materials from both sides of the traveling web by streams of air, of utilizing the air from said streams to maintain the sheet or web in proper relation thereto and of applying an auxiliary air stream to the web to maintain the web in proper position relative to said streams after the web has passed the streams and the surplus material has been removed.

8. The method of applying coating materials in semi-liquid form to a traveling web, which consists in applying to both sides of the web coating materials somewhat in excess oiactual coating requirements, of removing said surplus coating materials by means of streams of air positioned on both sides of the traveling web, of utilizing the air streams to maintain the traveling webin proper relation thereto and of expanding "the-air from said air streams to precipitate and remove coating materials from said air.

9. The method of applying coating materials in semi-liquid form to both sides of a traveling sheet or web, which consists in applying coating materials to both sides of the web, of directing streams of air against the web counter to its direction of travel, both for the purpose of smoothing said coating materials simultaneously over both sides of the web and of holding said web and the coating material thereon, free of mechanical contact with any part or the adjacent equipment. 10. The method of applying coating materials in semi-liquid form to both sides of a traveling web, which consists in applying coating materials to the web, of smoothing said coating materials over both sides 01' the web by directing streams of air against the web counter to its direction of travel, and without mechanical contact with said web or the coating material thereon, and of holding said web after the coating materials have been smoothed thereon, in a predetermined position relative to said aforementioned streams of air.

CABLE J. MERRILL. 

